Using observatories and telescopes to determine when the month begins and ends

Question: What is the Islamic way by which the beginning of the month is determined? Is it permitted to rely upon calculations of astronomical observatories to know when the month begins and ends? Is it permitted for a Muslim to use telescopes to know the moon sighting?

Response: The Islamic way of knowing when the month has entered is by people sighting the new moon. It should be done by people who are trusted in their religion as well as their physical ability to sight.

If they see the new moon, then the people must act upon the sighting by fasting if it was the new moon of Ramadhan, or ending the fast [of Ramadhan] if it was the new month of Shawwaal.

It is not permitted for a person to rely on the calculations of astronomical observatories in the absence of the sighting. However, if the sighting is confirmed through the observatories then it is valid, due to the generality of the statement of the Prophet (sal Allaahu alayhi wa sallam):

If you see it [the new moon], then begin your fasting, and if you see it, then end your fasting. [2]

As for mere calculations, it is not permitted to rely upon them nor act upon them.

With regards to using telescopes – which are lenses which magnify the new moon – there is nothing wrong with it however it is not an obligation. This is because what is apparent from the Sunnah is that a person should rely on a normal sighting and nothing else. However if a person used a telescope- to confirm his sighting – then this sighting is implemented.

In the olden days, people would use something similar when they would climb beacons [1] on the 30th night of Sha’ban or 30th night of Ramadhan; they would use this position to sight the new moon.

The point is that as long as the moon is sighted – using any type of medium – it is obligated to act upon such a sighting, due to the generality of the statement of the Prophet (sal Allaahu alayhi wa sallam):

If you see it (the new moon), begin your fasting; if you see it, end your fasting. [3]

Footnotes

[1] Beacon: A tower, hill or an elevated place used for sighting; it is also used to describe light-houses.
[2] Narrated by Abu Hurayrah; Collected by Al-Bukhaaree & Muslim